Competing structural instabilities in Bi2SiO5
Competing structural instabilities in Bi2SiO5
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DOI：
10.1103/physrevb.98.134102
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发表时间：
2018-10
影响因子：
3.7
通讯作者：
A. Girard;H. Taniguchi;S. Souliou;M. Stekiel;W. Morgenroth;A. Minelli;A. Kuwabara;A. Bosak;B. Winkler
中科院分区：
文献类型：
--
作者：
A. Girard;H. Taniguchi;S. Souliou;M. Stekiel;W. Morgenroth;A. Minelli;A. Kuwabara;A. Bosak;B. Winkler
通过 X 射线热漫散射 (TDS)、非弹性 X 射线散射 (IXS) 和 K 处铁电转变的密度泛函理论计算，研究了 的晶格动力学。沿着[100]方向观察到棒状扩散特征，垂直于准一维硅酸盐链的方向。沿 [100] 方向的声子色散的 IXS 测量将这些漫射特征与耦合不稳定的横向光学和声学分支相关联。在布里渊区边缘和点处也观察到了强烈的温度依赖性 TDS 信号，表明铁电和反铁电畸变之间存在竞争。我们用 IXS 观察到在该点处有大量但有限的声子软化，在该点处有轻微的软化，这与氧原子的位移有关。实验与理论 TDS 和 IXS 之间的良好一致性使我们能够对发生的各种晶格动力学不稳定性进行定量概述。铁电和反铁电序竞争的直接证据为通过施加压力或电场来调整其性质开辟了道路。
The lattice dynamics ofhas been studied by x-ray thermal diffuse scattering (TDS), inelastic x-ray scattering (IXS), and density functional theory calculations across the ferroelectric transition atK. Rodlike diffuse features are observed along the [100] direction, perpendicular to the direction of the quasi-one-dimensional silicate chains. IXS measurements of the phonon dispersion along the [100]direction related these diffuse features to coupled unstable transverse optic and acoustic branches. A strong temperature-dependent TDS signal was also observed at the Brillouin zone edges, at theandpoints, indicating a competition between ferroelectric and antiferroelectric distortions. We observed with IXS a substantial but finite phonon softening at thepoint and a minor softening at thepoint, that are associated with the displacement of oxygen atoms. The good agreement between the experiment and the theoretical TDS and IXS allows us to provide a quantitative overview of the various lattice dynamical instabilities occurring at. The direct evidence for competing ferroelectric and antiferroelectric orders opens the way towards tuning the properties ofby application of pressure or electrical field.